Divide words into their segments based on each sound. These sound segments are called phonemes. Phonemes are the basic form of a sound that is sensed in your head rather than spoken. Every word has at least one phoneme but these phonemes are not determined by the number of syllables or the number of letters in a word. They are determined by the number of sounds a word contains. For example, the word "bus" contains three phonemes: the initial consonant, the vowel and the final consonant.
Find the IPA symbol for each phoneme you've identified. Each phoneme has a corresponding IPA symbol that must be used. Sometimes, these symbols may appear similar or identical to English alphabetical letters. However, not every letter in the English alphabet has its own IPA symbol. Also, multiple letters can contribute to a single phoneme such as "ie" or "ch." Therefore, the phonemes must be based on sound.
Convert the phoneme to IPA by writing the symbol for each phoneme. For example, the initial phoneme in "been" is the familiar "b" IPA symbol and the final phoneme is the familiar "n." Vowels are more difficult because they are highly dependent upon tone, which can change. Changing a vowel's tone will change the entire word, such as "sin" to "sun." This is why vowels have their own section of the IPA chart. Carefully consider the vowel sound and find the corresponding IPA symbol.
Write the word in IPA. IPA guidelines require phonemes to be written in brackets to distinguish them from alphabetic symbols. The word "been" would be [bIn] in IPA. The brackets establish phonemes instead of letters, which is what allows the familiar "b" and "n" to be written and not confused with their alphabetic counterparts. Notice that a single character is used for the vowel sound even though "been" is spelled with two vowels. This is because there is only one vowel sound in "been."
Repeat the process for all of the words you wish to convert. If you wish to convert an entire sentence, you should make sure the entire sentence is in brackets. Formal punctuation required in English writing is not permissible in IPA. Therefore, do not capitalize the initial phoneme, as this will change the sound. For example, the letter "E" in IPA could be [e] or [E], but the former would be pronounced with a long A sound, as in "bait," while the latter would be pronounced as a short E sound, as it "bet." Periods, commas and other punctuation marks are not permitted.